In a networked environment such as the Internet, it is often desirable to pair one or more documents with a requested document, such as a web page. A document viewer's experience may be enhanced by content that is of interest to the viewer. For example, a requested web page may be displayed along with one or more additional content items. The content can be selected based on a variety of criteria, often with the end goal of soliciting a user reaction such as exploration of the content via a click-through.